Pseudolysogeny of Pseudomonas aeruginosa bacteria infected with φKZ-like bacteriophages

Abstract

In this work, a final piece of evidence proving that bacteria Pseudomonas aeruginosa are capable of transition to the pseudolysogenic state after infection with phiKZ-like phages has been produced. It was shown that the decisive factor in this process is multiple infection of bacteria with bacteriophages belonging to this genus. In the course of this work, stable clinical isolates of bacteria liberating novel bacteriophages of this genus (Che2/2 and Che21/5) were detected and attributed to species phiKZ and EL, respectively, according to their phenotypic characters and the results of DNA analysis. For three bacteriophages belonging to species EL (EL, RU, and Che21/5), mutants with disorders in the capability for pseudolysogenization were isolated. One of the mutants of phage EL possesses properties of virulent mutants of typical temperate phages (vir mutant). This mutant fails to form pseudolysogens and, moreover, provides the effect of dominance upon coinfection of bacteria with the wild-type phage EL, but however is unable to exhibit this effect upon joint infection of bacteria with wild-type phages of species phiKZ and Lin68. It is assumed that the effect of pseudolysogeny may be connected with functioning of phiKZ and EL genes that control the products similar to repressors of other phages. Because earlier wild-type phiKZ-like phages were shown to be present in commercial phage-therapeutic preparations (which represents certain problems), it is expedient to use virulent mutants of phages belonging to this genus rather than phages of the wild type.